Roofing products include shingle, metal, wood shake, clay tile, concrete tile, slate, or membrane. Each has its own limitations. Shingle roofing using asphalt in the base is common, inexpensive, and has two layers of shingles over the entire roof area. Metal roofing is made up of various types of metals such as steel, aluminum, and copper. Wood shake roofing, desired for its look but not durability, absorbs water creating moisture and can be flammable. Concrete tile and clay tile are heavy in weight. Slate roofing can be expensive and the tile may shatter around a nail hole.
Membrane roofing is generally used on flat or nearly flat roofs to prevent leaks and move water off the roof. Membrane roofs are most commonly made from synthetic rubber, thermoplastic polymers such as polyvinyl chloride (PVC) and thermoplastic polyolefin, or modified bitumen. Roofing membrane may replace asphalt roof systems or an older, less effective type of flat roofing system. Membrane roofs become more common in residential application, but are more commonly used in commercial application.
Roofing membranes are fabricated from strong, flexible, waterproof materials. They may be applied in multiple layers may consist of a single-ply membrane. Membranes usually contain a fabric made from felt, fiberglass, or polyester, for strength, which is laminated to or impregnated with a flexible polymeric material. The polymeric material may include bituminous hydrocarbon materials such as asphalt, to synthetic rubber (e.g., EPDM), or PVC. The color of the polymer itself ranges from black to white, often depending on the amount of coloring agent (e.g., carbon black) present.
PVC is mixed with one or more heat stabilizers, lubricants, plasticizers, fillers, or other additives to make more processable, all of which can influence its physical and mechanical properties.
Adding insulation makes a building more energy efficient and acts as a sound absorber or barrier, keeping noise levels down. Insulation includes use of blankets, loose-fill, or rigid systems with materials such as rock wool, fiber glass, cellulose, polyurethane foam, extruded polystyrene foam, expanded polystyrene foam, polyurethane foam, polyisocyanurate foam, or combinations of two or more thereof. Such insulating material is often used together with roofing membranes using PVC.
Frequently, a plasticizer in PVC migrates or leaks out thereby rendering the foam ineffective or less effective. It is therefore desirable to prevent liquid plasticizer in PVC roofing membranes from migrating into insulation.